Comparison among estimation methods of C* parameter for axially oriented external surface crack in cylinders.

C* is usually used to describe the creep crack growth. ASTM E1457 allows C* to be calculated from creep load line displacement rate. However in components it is difficult or impossible to measure load line displacement rate. Therefore for the components C* must be determined by finite element methods or reference stress concepts. Estimates of C* obtained by reference stress methods will depend on the collapse mechanism adopted and therefore several estimations are proposed. This paper presents a numerical study of non-linear fracture mechanics parameter predictions under elevated temperature for axially oriented external surface crack in cylinder. Comparison of C* calculated from FE analysis and different reference methods is conducted. The values of C* obtained from the API579 net section solution are also found to be slightly conservative and give the closest agreement to the F.E. contour integral C*. In addition, the comparison between C* of homogeneous material and TYPE IV cracking is conducted. The difference between homogeneous material and TYPE IV cracking is almost negligible and therefore the reference stress solutions for homogenous material could be applied to estimate C* for TYPE IV cracking. [ABSTRACT FROM AUTHOR]